Currently the primary propulsion of craft that is generally applicable to all environments such as in air or space is rocket propulsion. While used with moderate success, this method has been commonly known to have serious limitations. The need to eject mass at high velocities requires enormous energy and the mass needs to be supplied by the craft, particularly if no substance is available from the environment (for example, in the vacuum of space). As distance and velocity requirements increase, the percentage of the weight of the craft that must be allocated to fuel storage becomes unacceptably large. Even when the craft is not accelerating, for example, if hovering at some constant distance from the ground, a large amount of energy still has to be expended to maintain position.